This invention relates to a novel air curtain device suitable for use in detecting certain characteristic vapours emitted from objects positioned therein.
Vapours emitted from the more common explosive materials and certain other contraband substances, unless masked or hermetically sealed, can be detected even though concealed, using known vapour trace techniques. When explosives are carried by a person, for example, the individual's clothing and body becomes rapidly contaminated by the explosive's vapour. This is also true with respect to personal effects in luggage when subjected to vapours emitted from a concealed bomb. Accordingly, vapour detectors or "sniffers" are an acknowledged security instrument, particularly in view of the upsurge in terrorist bombings of buildings, aircraft and the like. Their principal use and application is where a large number of personnel or other objects must be quickly screened such as is normally encountered at airport terminals.
One major drawback inherent in vapour detectors used in screening personnel is the fact that each person must be subjected to individual search. Personal search is unacceptable to many and is of major concern to airport supervisors and attendants charged with the responsibility of orderly and rapid air-traveller and luggage processing.